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Old 20-01-2015, 08:47   #1
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Strange solar panel problem

We have four Kyocera KC120 panels that were bought and installed in 1998. Up until this week, they have worked flawlessly without a thought given to them.

One of the panels has ceased providing current. Here is the problem:
1. Voc across the leads is 21V as expected.
2. Isc is zero.
3. Vpm is 17.4V as expected
4. Ipm is zero.

Here is what I have found:
1. There are 6 bypass diodes arranged in two banks of three. The panel cells appear to be divided in half with these. All diodes test OK.
2. If I put a jumper wire across one bank of diodes, no change in output occurs.
3. If I put a jumper across the other bank, a lot of current flows back INTO the panel.

I suspect I have an internal open or short circuit in one half of the panel, or where that half feeds its diode bank. Nothing is obvious from the foil traces that can be seen on top, and the bottom is all potted and sealed.

Anyone have any ideas?

Mark
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Old 20-01-2015, 13:42   #2
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Re: Strange solar panel problem

Sounds to me like an open between solar foil connector sections.
Jumping the half where lots of current back into the panel would probably be the half where the problem lies.
How much current is "lots"?
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Old 20-01-2015, 14:01   #3
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Re: Strange solar panel problem

Not knowing exactly how the total circuit is arranged, I would suggest trying to test the diodes without them actually hooked up to the panel.
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Old 20-01-2015, 15:33   #4
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Re: Strange solar panel problem

Quote:
Originally Posted by senormechanico View Post
Sounds to me like an open between solar foil connector sections.
Jumping the half where lots of current back into the panel would probably be the half where the problem lies.
How much current is "lots"?
Yes, that has been my thought, but I don't see any obvious issues and the foil connectors all appear to be on top and visible. "Lots" means the full 6A output of the panel it was connected in parallel to.

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Old 20-01-2015, 15:33   #5
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Re: Strange solar panel problem

Quote:
Originally Posted by Garrettw View Post
Not knowing exactly how the total circuit is arranged, I would suggest trying to test the diodes without them actually hooked up to the panel.
Yes, that is how I tested them - removed all of them and tested individually. They all test fine. I was so hoping that they were open...

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